it will make you build much easier if you get matching parts, especially for the first build what component group are are you thinking? you will need to match the BB to the crankset you use

UK online shops used to have great deals but that is going away (ultegrat $800 one left https://www.ribblecycles.co.uk/shima...uble-groupset/)

it is almost always more expensive to build you own (unless you have a large stash of parts) than to buy a complete bike.......that is info, not meant to deter you from the path